This invention relates to drawing tools and, more particularly, to multipurpose drawing tools enabling the user to draw circles, to draw and measure lines, to construct and measure angles, and to produce geometric constructions and patterns.
There are numerous drawing tools available in the prior art for drawing circles, drawing and measuring lines, constructing and measuring angles, and producing geometric constructions and patterns. Generally, these devices do not provide clearly visible, direct views of vertex points through an open pivot point for drawing circles, constructing and measuring angles, and producing geometric constructions and patterns. Rather, the user must approximate the positioning of the device over the vertex point, impairing the accuracy of the positioning of circles drawn with the device, or the accuracy of the construction and measurement of angles.
Additionally, even where devices are provided which can be used in performing all of the above functions, the devices require numerous parts, which make them expensive to construct and easy to damage. Where the devices are provided with adjustable radius indicators, i.e., movable parts which must stay put once positioned, the prior art devices are slow and cumbersome to use, and can be inaccurate.
Accordingly, an object of the present invention is to provide a drawing tool which provides an open pivot point providing a direct view of vertex points on drawing surfaces positioned under the tool;
It is another object of the present invention to provide a simple, inexpensive and easy-to-assemble drawing device for drawing circles, drawing and measuring lines, constructing and measuring angles, and producing geometric constructions and patterns;
Yet another object of the present invention is to provide a drawing tool with a movable radius indicator which is accurate and will stay put once positioned without a separate locking mechanism which must be manipulated once the indicator is in the desired location; and
A still further object of the present invention is to provide a drawing tool having an elongated position for measuring and drawing lines and a protractor portion for measuring angles.
The present invention comprises a multi-purpose drawing tool including a protractor portion at one end and an elongated radius arm portion at the other end. An adjustable radius indicator, which is mounted in an elongated cavity for movement along the elongated radius arm portion, includes spring portions biased against the sides of the elongated cavity and pressure dimples riding in and engaging slots running alongside the elongated cavity to resist unintended indicator movement. The indicator rides in elongated slots in the bottom of the first member and along upstanding elongated ridges in the top of the first member. The drawing tool also includes dimples in its underside to prevent smudging of markings already on a drawing surface positioned below the tool.